Response of flying-foxes to heat stress

Flying-foxes are vulnerable to periods of extreme heat: panting, fanning, shade seeking, and then with mass fatalities reported at temperatures of 43° C and above.

However, in the Ku-ring-gai flying-fox reserve, the flying-foxes react to days of high temperature by moving to different areas of the reserve where the temperature is lower and the humidity is higher.

The current roost location at the northern extent of the reserve appears to be particularly vulnerable to extreme heat (although it’s obviously a good place to hang at any other time); so on hot days (> 35° C) the flying-foxes move further along the flat and down into the valley where it is more sheltered. On days of extreme heat (> 38° C) the flying-foxes totally abandon their normal roost and spread along the creek line, hanging low in the trees.

Environmental monitoring has shown that along the line of Stoney Creek on a hot day it’s typically 2-3° C cooler, and 5-10% higher in humidity, than in the normal camp area.

(Click anywhere on the map below to view larger version)

Movement of flying-foxes in Ku-ring-gai Flying-fox Reserve, Gordon, in response to periods of high heat. Areas shown are: (white) average normal extent of the camp over the last four years; (yellow) extension of the camp to the South West on a 35 ° C day; and (red) approximate extent of the camp on a day of > 40 ° C temperatures.